Planar supported lipid bilayers have attracted immense interest for their properties as model cell membranes and for potential applications in biosensors and lab-on-a-chip devices. We report the formation of fluid planar biomembranes on hydrophilic silica aerogels and xerogels. Scanning electron microscopy results showed the presence of interconnected silica beads of approximately 10-25 nm in diameter and nanoscale open pores of comparable size for the aerogel and grain size of similar to36-104 nm with similar to9-24 nm diameter pores for the xerogel. When the aerogel/xerogel was prehydrated and then allowed to incubate in L-alpha-phosphatidylcholine (egg yolk PC) unilamellar vesicle (similar to30 nm diameter) solution, lipid bilayers were formed due to the favorable interaction of vesicles with the hydroxyl-abundant silica surface. Lateral mobility of labeled lipid N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)-1,2-dihexadecanoyl-sn-glycero-3-ph osphoethanolamine was retained in the membranes. A diffusion coefficient of 0.61 +/- 0.22 mum(2)/s was determined from fluorescence recovery after photobleaching analysis for membranes on aerogels, compared to 2.46 +/- 0.35 mum(2)/s on flat glass. Quartz crystal microbalance-dissipation was utilized to monitor the kinetics of the irreversible adsorption and fusion of vesicles into bilayers on xerogel thin films.